Beamline X12-B is a bending-magnet beamline operated by the Biology Department of Brookhaven National Laboratory, under funding from the Office of Biological and Environmental Research (OBER) of the Department of Energy. M. Capel is responsible for the facility. The beamline has a horizontal acceptance of 3.5 mrad from a bending magnet, double focusing optics, and a fixed-exit, Si (I 11) monochromator to provide a stable, high intensity beam over the spectral range between 7.6 and 13.1 KeV. The beam's focal spot size is 300 gm FWHH along both axes. A maximum flux of _ 1012 xph/sec is deliverable on sample. Since the bean-dine was designed for small-angle diffraction, much emphasis was placed on designing and implementing an effective beam-collimation system. This, in conjunction with mature beamline control systems, provides a stable, brilliant beam and a low scattered xray background "). The following figure shows the optical train and diffractometer mechanism of the beamline.